The production of a laboratory atomic oxygen beam is useful in a variety of applications. For example, researchers need to simulate the flux and energy of atomic oxygen encountered by space vehicles in the upper atmosphere. The high chemical reactivity of this atomic oxygen flux causes substantial degradation of organic materials, thereby resulting in reduced material lifetimes. Also, such an atomic oxygen beam may be used in the calibration of mass spectrometers and other detection systems which are utilized in determining the densities of the gases within the flight envelope of spacecraft in low Earth orbit. Other applications include studying the kinetic properties of atomic oxygen as it collides with other molecules, determining drag coefficients, and studying basic interaction between atomic oxygen and surfaces.
Currently, numerous methods are used to generate atomic oxygen beams. For example, radio frequencies or microwaves excite an oxygen bearing gas to create a gas discharge which includes atomic oxygen and other species. Second, oxygen molecules are heated in the vicinity of a surface until oxygen atoms are thermally dissociated. Third, electrons are impacted against an oxygen bearing gas to create oxygen ions, which are mass separated and neutralized to atomic oxygen by a charge transfer cell. All prior methods share a combination of the following problems: low flux density, low mean energy, wide eergy distribution, numerous excited states of oxygen and accompanying gases, and synergistic reactions from different species. More significantly, these methods result in a high contamination background density of molecular oxygen or other gas products which distort the true interaction between the atomic oxygen and the sample material. For example, if the background pressure is 1.times.10.sup.-6 Torr, the entire surface of the sample is covered in one second by gases such as CO and molecular oxygen, thereby preventing a clear distinction between the effects of these reactive gases and atomic oxygen.
Accordingly, it is a primary object of this invention to generate an atomic oxygen beam which closely simulates low Earth orbit conditions.
It is a further object of this invention to accomplish the above object without the contamination which is characteristic of the prior art.
Other objects and advantages of this invention will become apparent in the specification and drawings which follow.